A biofilm is a community of microorganisms, such as bacteria, that are attached to a solid surface. The microorganisms in a biofilm form a matrix structure, and can be highly resistant to antibiotics. Molds can produce various allergens, irritants, and toxic substances, which can cause various health problems. The unwanted growth of organisms such as biofilm and/or mold can be a major problem for various situations. For example, in heating, ventilation, and air conditioning (HVAC) systems, such growth can occur on air filters, the interior of duct work for the air flow, water pipes, and/or the like. Similarly, such growth can occur on various surfaces and utensils within eating establishments, kitchens, bathrooms, hospitals, etc. Infections that at least in part are caused by these organisms account for many otherwise avoidable illnesses and even deaths each year.
Ultraviolet radiation has been shown to damage proteins and membranes in biofilms. Ultraviolet radiation having a longer wavelength (e.g., 320-400 nanometers) may damage cell DNA by creating reactive oxygen compounds, such as H2O2, O2, etc., which cause single strand breaks in DNA. Ultraviolet radiation having a shorter wavelength (e.g., 290-320 nanometers) is absorbed by DNA and proteins and alters nucleotides, while ultraviolet radiation of a very short wavelength (e.g., 100-290 nanometers) exhibits the strongest germicidal effects.
To this extent, ultraviolet radiation has been successfully used in the purification (e.g., sterilization) of various media, such as air, water, and food. In general, it is desirable that the ultraviolet radiation comprises wavelength(s) that are close to the absorption peak(s) of biologically significant molecules of DNA and/or proteins of a target impurity. For example, impurities, such as a bacterium, a virus, a protozoan, a germ, etc., comprise DNA/proteins having corresponding absorption peaks. By exposing the DNA/proteins to ultraviolet radiation having a wavelength close to the absorption peak(s) for a sufficient time and at a sufficient power, the impurity is destroyed. To this extent, exposing a medium that includes one or more of these impurities to sufficient ultraviolet radiation can destroy some or all of the impurities. When sufficient impurities are destroyed, the medium is purified to a safe condition.
Typically, the source of the ultraviolet radiation in a purification system is a mercury lamp. To this extent, a low-pressure or a medium-pressure mercury lamp provides a linear spectrum of radiation with one or more peak lines having a wavelength that is in the relative vicinity to the DNA absorption line. For example, a low-pressure mercury lamp having a main peak at 253.4 nanometers (nm) is generally used in low-consumption residential water purification systems and residential air purification systems. Further, a medium-pressure mercury lamp having a higher radiation power and a multi-peak radiation spectrum is used in municipal systems with medium and high water consumption.
However, the use of a mercury lamp as the source of ultraviolet radiation has significant drawbacks. For example, mercury is an extremely dangerous element, thereby limiting the applications of mercury-based water and/or air purification systems. In particular, such a mercury-based water purification system is generally not used in transportation or individual applications. Further, a typical lifetime of the mercury lamp generally does not exceed ten thousand hours. Still further, the radiation spectrum of the ultraviolet radiation generated by the mercury lamp includes peak lines having characteristic wavelengths that do not exactly coincide with the absorption peaks of DNA and proteins and these peak lines cannot be controlled or adjusted, which results in a decrease in the efficiency of the system. Still further, mercury lamps are fragile and bulky, which generally adds to the overall cost and/or size of the system and does not allow for a flexible design. Various other limitations are present as will be recognized by one of ordinary skill in the art.
In view of the foregoing, a need exists to overcome one or more of the deficiencies in the related art.